Recently purchased a S&W M&P 15-22, I have put approximately 300 rounds downrange. At first all seemed well, tried to zero the iron sights and it progressively shot worse. The pattern was sometimes ok, somestimes wild flyers. Cleaned the gun and noticed some tightness near the bolt end of the gun. Noticed what looked like fouling. Back to the range, same issues only worse. Broke it down for close inspection again, ran a brush down the barrel and it was extremely tight again. Used a Hoppes solvent and pad, it became logdged in the barrel again near the bolt again only this time terminally stuck. Used soft taps from muzzle end to dislodge the cleaning flute only to find a wad of lead fall out. A large clydrical piece of accumalated lead that blew my mind as to how large it was and odd shaped, looked like the bullets were slivering off a little piece at a time until the end result described. I have thoroughly cleaned it a the barrel looks great, clean as a whistle with no areas of fouling.

Has anyone heard of this happening before? What do you think may have caused it?

Novice to the shooting arts of AR styled guns but love this gun, any help is appreciated.

Merry Christmas. Its sounds like a bad bullet did disintegrate in the barrel leaving enough lead to cause the problem you had. Scarey situation. lucky that it wasn't worse. I would test fire it one round at a time & do a visual inspection after each shot to make sure the problem isn't caused by the rifle. Check each round before it is chambered to see if its ammo related & /or call S&W for expert advice. I shot 300 plus rounds through mine with about 1 jam up per 25 rounds for the first 100 or so rounds but no issues after that since. I did remember I had one jam & when I ejected the cartridge the bullet was bent on an angle. This was with Winchester 22lr varmint ammo. Rifle seems flawless now. Perhaps a break in issue??
Be cautious.

I will be cautious and try one round at a time then inspect. I just had a bad experience with my model 70 remington 270 rifle. It seems a cartridge exploded in the chamber blowing out the bottom portion of the magazine through the wood. Very lucky to have shooting glasses on, just a few wood splinters in the face and finger. It is being tested by remington to find the cause. It seems I have some bad mojo with ammo these days. I am not making this stuff up, really. Thanks again for your input, LG

Merry Christmas to all. I'm also new the the AR platform in general and the 15-22 specifically but what amazes me the most is how picky this riffle can be when it comes to the type of ammo used. I personally have stayed away from Remmington after reading the owners manual even though I use their ammo in my 9's with no problem what so ever. I have tried several brands and types within brands since I joined the 15-22 club with the worst experience coming after using Winchester m22. Nothing compared to what you described. I hope your next trip goes much better. I'll stick with the federal and CCI and hopefully never have to deal with a day like you just had. I'm glad your ok and have a safe and happy new year!

I am going to use cci mini mags, I was told the Rem I bought would be ok. After a couple hours of cleaning the barrell looks great. Rifled from muzzle to breech. Thanks for the input from all, nice to have a base of knowledge and experience to rely on.

At the range today, I listened to all of the posts received and had awesome results. CCI mini mags performed well, no problems. Test fired one at a time then inspect, very little fouling and no change in the appearance of the barrel. Swabbed clean and put a few downrange with great results. This gun is so much fun to shoot, zeroed in my holo sight quickly and enjoyed some freestyle plinking. Cannot wait to shoot it again. Thanks to all for the advice and comments.